This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Non-heme iron halogenases are found as tailoring domains in NRPS systems. They belong to the cupin family of non-heme iron proteins and have striking similarities to non-heme iron hydroxylases yet are very specific in their reactivity. To understand the reactivity of nonheme iron halogenases, we have solved a structure of halogenase with a closed active site and one with an open active site. The comparison of these structures helps us to understand which residues are important for halide binding. We are also attempting to solve the first structure of a nonheme iron hydroxylase from an NRPS pathway so that we can make direct comparisons with the nonheme iron halogenases.